The contact of blood with biomaterials often results in the formation of blood microemboli, which can block microvessels and cause organ damage in the blood recipient. An in-vitro test has been developed by the principal investigator to measure effective microemboli concentrations in blood by passing the blood through micropore filters. To calibrate the filter test and to study the effects of microemboli on organ flow, studies are currently being conducted in which microemboli-laden blood is perfused through cat-hindlimbs at constant pressure and the flowrate curves are recorded. The objective of the proposed study is to incorporate pulsatile pressure into the hindlimb-perfusion experiments and to determine the effects of physiologic pulsatile pressure on blood flow restriction by microemboli. A pump-controller will be constructed to maintain a physiologic pulsatile-pressure pattern while driving blood at a variable flowrate. Blood containing microspheres or biomaterial-induced microemboli will be perfused through cat hindlimbs with a pulsatile-pressure driving force. The blockage of the hindlimb vessels, determined from computer analysis of the flowrate curves, will be compared with vessel blockage during non-pulsatile (constant-pressure) hindlimb perfusions.